Classical Greece: City-States, Alliances and Macedonian Expansion

Greek forces defeated Xerxes’s invasion at Salamis in 480 BC and Plataea in 479 BC. Athens then led a maritime alliance while Sparta headed a land coalition. Their war of 431–404 BC ended with Athenian defeat. Thebes later broke Spartan dominance at Leuctra in 371 BC, before Philip II’s victory at Chaeronea in 338 BC established Macedonian leadership.

Athens gave adult male citizens direct participation in its Assembly and relied on a large fleet. Sparta’s narrower citizen body maintained its standing through helot labour and military training. Persian kings supported competing Greek powers through diplomacy and finance after the invasion campaigns ended.

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Persian rule and the formation of Greek coalitions

Greek cities in Ionia, on the Aegean coast of Asia Minor, had come under Persian rule by the middle of the sixth century BCE. In 499 BCE, the Ionian cities rebelled. Athens and some other Greek communities sent assistance, but the revolt was defeated in 494 BCE. Persian control over the cities of Asia Minor was restored, and the revolt gave the Persian king an additional reason to intervene in mainland Greek affairs.

Persian campaigns followed. In 492 BCE, Mardonius led an expedition through Thrace and Macedonia, while a storm wrecked much of the supporting fleet near Mount Athos. In 490 BCE, a Persian force landed in Attica. The Athenians, supported by 1,000 Plataeans, defeated it at Marathon. The Persian fleet then approached Athens but did not attack after finding the city defended.

The second invasion, launched by Xerxes I in 480 BCE, was more extensive. Persian land forces moved through Thrace, Thessaly and Boeotia while a large fleet supported their advance. A Greek coalition attempted to block the routes by land and sea. The Spartan king Leonidas led the defence at Thermopylae, while Greek ships fought at Artemisium. The Persians eventually entered Attica and burned Athens, but the Athenians had evacuated the city by sea. At Salamis, the Greek fleet used the narrow waters to reduce the Persian numerical advantage and defeat the invading navy. A Greek victory at Plataea in the following year completed the main defeat of Xerxes’ invasion.

The wars also changed the balance among the Greeks. A common Hellenic coalition had included Sparta and Athens during the invasion, but the end of the immediate Persian danger removed much of the reason for continued unity. Athens led a new alliance, later known as the Delian League, whose stated purpose was to continue the struggle against Persian control of Greek communities. Its treasury was kept on the sacred island of Delos. Sparta withdrew from active leadership, allowing Athens to build a naval and commercial power in the Aegean.

Athens enforced contributions and punished attempts to leave the Delian League. Sparta’s older alliance centred on Peloponnesian communities and its land army. Both coalitions gave leading cities influence over their members.

Athens and the political organisation of a polis

Athens’ power rested partly on institutions that gave its male citizens a direct role in public decisions. After the overthrow of the tyrant Hippias in 510 BCE, Cleisthenes’ reforms reorganised Athenian civic life. The territory was divided into demes, local civic units that became the basic elements of citizenship. Ten tribes were constructed from coastal, urban and inland areas, so that each combined communities with different local interests rather than reproducing a simple division between the city, the coast and the countryside.

Athens expanded participation through its Assembly and citizen courts. Women lacked political voting rights, while resident foreigners and enslaved people held separate legal statuses. Athenian democracy explains these institutions.

Athens’ naval strength connected public finance, military service and political influence. Revenue from the silver-producing district of Laurion helped fund the fleet before the Persian invasion of 480 BC. Triremes also required crews, maintenance and continuing expenditure; poorer citizens could serve as rowers without supplying the equipment of a hoplite. The links between silver, ships and labour are explored in Greek mining and Greek navies.

The Peloponnesian War and the limits of Athenian power

The rivalry between the two coalitions eventually produced the Peloponnesian War, which began in 431 BCE. The conflict was not simply a contest between Athens and Sparta. Athens commanded the Delian League and Sparta led its allies, so the war involved many city-states with different strategic interests. Athens was primarily a naval power, while Sparta was stronger on land. This made it difficult for either side to force a rapid decision.

Several disputes brought the conflict to a head. Corinth, a Spartan ally, fought with its colony Corcyra over Epidamnus. Corcyra then sought an alliance with Athens and offered the use of its navy, which was one of the largest in Greece. Athens also became involved in a dispute over Potidaea, and its decrees restricting Megarian trade were treated by Sparta and its allies as violations of the Thirty Years Peace. Behind these immediate issues lay a larger concern: the growth of Athenian power and the resentment it created among states that feared its control.

Sparta’s early strategy was to invade Attica. The Athenians withdrew behind their walls, while their fleet carried troops and attacked elsewhere. An outbreak of plague inside Athens caused many deaths, including that of Pericles. Neither side gained a decisive advantage, and the Peace of Nicias in 421 BCE temporarily ended the first phase of the war.

Hostilities resumed after conflict involving Sparta, Athens and Argos. Athens then undertook a more ambitious policy. It attacked Melos, an island that had remained outside the Delian League, and in 415 BCE supported a major expedition to Sicily. The Sicilian expedition was prompted by a request from Segesta and was directed against Syracuse’s position in the wider conflict. It ended disastrously: the Athenian force was lost, Nicias was captured and executed, and Athens suffered one of its most severe defeats.

The disaster weakened Athenian control but did not immediately end the war. Persian financial assistance enabled Sparta to build a fleet capable of challenging Athens at sea. Sparta also used the strategic importance of the Hellespont, through which Athens obtained grain, to threaten the city’s supplies. After the Athenian fleet was defeated at Aegospotami in 405 BCE, Athens could no longer continue effectively. In 404 BCE it surrendered, losing its walls, fleet and overseas possessions. Sparta installed an oligarchic government known as the Thirty Tyrants, though democracy was later restored.

Fourth-century struggles for hegemony

The King’s Peace of 387/386 BC confirmed Persian control over Greek cities in Asia and proclaimed autonomy for other Greek cities, with specified exceptions. Sparta used its enforcement to challenge rival federations.

Sparta pressed Thebes to dissolve the Boeotian confederacy. Its forces later seized the Cadmea fortress, giving Sparta direct control over the city until Theban resistance overturned the occupation.

Theban resistance eventually overturned that arrangement. In the 370s, Pelopidas and Epaminondas helped restore Theban power and reorganise the Boeotian League. The league joined communities under federal institutions and could mobilise infantry and cavalry on a regional scale. Thebes also developed a more effective army, drawing on military methods associated with Epaminondas and Pelopidas. In 371 BCE, at Leuctra, the Thebans defeated the Spartan army. The victory ended the long period of Spartan military dominance.

Thebes did not establish a durable replacement for Spartan power. Its armies intervened in the Peloponnese, weakened pro-Spartan governments and supported the liberation of helots in Messenia, where a new centre was established. Thebes also sought influence through wider confederations. Yet its authority depended heavily on its leading commanders. Epaminondas’ death at Mantinea in 362 BCE, after a Theban victory over a coalition including Athens and Sparta, left no equivalent political force to maintain Theban supremacy.

Athens meanwhile attempted to rebuild its position through a Second Athenian League. It avoided the earlier League’s formal tribute system and relied instead on contributions collected for particular military needs. Nevertheless, Athenian generals could still pressure allies, and the arrangement again appeared to reproduce elements of the earlier Athenian empire. When allies revolted between 357 and 355 BCE, Persian pressure forced Athens to recognise their independence. The collapse of the league further reduced Athens’ ability to act as a major power.

After 362 BCE, no Greek city could impose lasting hegemony over the rest. Sparta had been weakened, Athens lacked the resources to recover its former naval position, and Thebes had lost its principal leader. Persian kings continued to influence Greek disputes, while rival confederations and civil wars produced repeated instability.

Macedon enters Greek affairs

Philip II became king of Macedon in 359 BC. He reorganised the army and expanded royal territory through campaigns and agreements with neighbouring rulers.

Philip first consolidated Macedonian authority and expanded against the Paeonians, Thracians and Illyrians. He captured Amphipolis in 357 BCE, taking an important Athenian trading port at the mouth of the Strymon River, and seized Pydna a year later. These gains brought Macedonian power closer to Athenian interests. The Phocian War gave Philip further opportunities to intervene in central Greek affairs. Athens was divided between those who urged resistance, including Demosthenes, and those who believed that avoiding a direct confrontation was safer.

Philip combined trained spear-bearing infantry with cavalry and siege operations. He defeated Athens and Thebes at Chaeronea in 338 BC and established the League of Corinth under Macedonian leadership.

Alexander and the transition to the Hellenistic world

Philip was assassinated in 336 BCE, and his son Alexander succeeded him. Alexander secured the Macedonian throne and the position of leader of the Hellenic League. The destruction of Thebes demonstrated the consequences of resisting Macedonian authority, while Athens ultimately accepted peace. The Greek communities remained politically distinct, but Macedonia now controlled the framework within which their external policy operated.

The conquests that followed under Alexander, and the competing kingdoms that formed after his death, belong to the Hellenistic world. They extended Greek political, military and cultural activity far beyond the settings of the fifth-century city-states.

In 334 BCE, Alexander crossed the Hellespont with approximately 30,000 infantry and 5,000 cavalry. He conquered the Achaemenid Persian Empire through a series of campaigns that included victories at Granicus, Issus and Gaugamela, as well as the siege of Tyre. His power reached Egypt and territories as far east as the fringes of India.

Alexander died in Babylon in 323 BCE while planning further campaigns. His empire was then divided among his successors, the Diadochi. That fragmentation marks the conventional end of Classical Greece and the beginning of the Hellenistic period. The city-states continued, but the era in which Athens, Sparta and Thebes competed to direct the Greek world had given way to a political landscape dominated by large kingdoms.